A lexical knowledge base is a computer-readable body of information about words, including a network of semantic relations between words. Each semantic relation is a unidirectional link between two words labeled with a particular semantic relation type that relates the meanings of the two words. For example, semantic relation (1) below indicates that the meaning of "wheel" is related to the meaning of "car," in that a wheel is a part of a car: EQU wheel.rarw.Part-car (1)
Semantic relations each have one of a number of standard relation types, such as: Cause, Domain, Hypernym, Location, Manner, Material, Means, Modifier, Part, Possessor, Purpose, Quasi-Hypernym ("Quespernym"), Synonym, Time, TypicalObject, TypicalSubject, and User. Semantic relations may be chained together to form semantic relation paths ("paths") relating the meanings of two words via one or more intermediate words. For example, path (2) below indicates that one of the ways that the meaning of "spin" is related to the meaning of "car" is that a wheel is a part of a car and that a wheel is typically spun: EQU spin-TypicalObject.fwdarw.wheel.rarw.Part-car (2)
Semantic relations and semantic relation paths are useful in a broad range of natural language processing applications to identify direct and indirect relationships in meaning between pairs of words. For example, natural language parsers use this information to disambiguate the meaning of a sentence.
While useful lexical knowledge bases contain many semantic relations, even the most complete lexical knowledge bases omit some valid semantic relations. The ability to determine whether a semantic relation is valid even though it is not explicitly contained in a lexical knowledge base would therefore have significant utility.